/*
  a pagefault benchmark
  kazutomo@mcs.anl.gov
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <sys/mman.h>
#include <sys/time.h>


static double gettime(void)
{
  struct timeval tv;
  gettimeofday(&tv, 0);
  return (double)tv.tv_sec + (double)tv.tv_usec/1000.0/1000.0;
}


static void test_pagefault(int mode, size_t bufsize )
{
    char *p;
    double t1,t2;
    int i, pagesize = getpagesize();


    printf("pagesize: %d bytes\n",  pagesize);

    t1 = gettime();
    if( mode==0 ) {
      p = mmap(NULL, bufsize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
      assert( p );
    } else {
      p = malloc( bufsize );
      assert( p );
      if( mode == 1 )  for(i=0;i<bufsize; i+=pagesize) p[i] = 0;  // prefault
    }
    t2 = gettime();
    printf("alloc: %lf sec\n", t2-t1);
    if( mode < 2 )
      printf("pagefault: %lf usec\n", 
	     (t2-t1)/(double)(bufsize/pagesize) * 1000.0 * 1000.0 );

    for(i=0; i<3; i++) {
      t1 = gettime();
      memset(p, 0, bufsize);
      t2 = gettime();
      printf("memset: %lf sec => %lf MB/sec\n",
	     t2-t1,
	     (bufsize/(t2-t1))/1024.0/1024.0 );
    }      

    t1 = gettime();
    if( mode == 0 ) {
      munmap( p, bufsize );
    } else {
      free(p);
    }
    t2 = gettime();
    printf("free: %lf sec\n", t2-t1);
}


int main(int argc, char **argv)
{
  int mode=0;
  int bufsize = 10*1024*1024;

  if( argc < 2 ) {
    printf("Usage: pftest mode [bufsize]\n");
    printf("\n");
    printf("mode=0: mmap with MAP_POPULATE\n");
    printf("mode=1: malloc and a simple prefault loop\n");
    printf("mode>1: malloc\n");
    printf("\n");
    exit(1);
  }

  mode = atoi(argv[1]);
  if( argc > 2 ) {
    bufsize = atoi(argv[2]);
  }

  printf("mode: %d\n", mode);
  printf("bufsize: %d\n", bufsize);

  test_pagefault(mode, bufsize );

  
  return 0;
}